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How do genes affect the way drugs work?
In December 2008, the New York Times ran a story about a woman from California who had been taking a drug called tamoxifen to help prevent breast cancer. After two years of taking the drug, her doctor ordered a new genetic test that showed that her genes were preventing the drug from working properly.
“You find out you’ve been taking this medication for all this time, and find out you are not getting benefit…I was devastated” says the women. She had to stop taking tamoxifen. The good news is that she found out that the drug was not helping her and her doctor can now prescribe a drug which will work in her body. The bad news is that she could have known this two years ago if she had taken the genetic test from Day 1.
Experts report that approximately $300 billion is wasted each year on drugs which apparently do not work in people who have certain genes. These people never receive the full benefit from these drugs. Others are getting dangerous side effects.
For example, the blood-thinning drug warfarin is one of the top twenty drugs prescribed in the US. It is used to help prevent blood clots. If a person’s genes prevent the drug from working correctly, warfarin becomes dangerous. It is one of the top three drugs that cause hospitalization or emergency room visits. If a person has genes that allow too much warfarin to get into the bloodstream, the blood cannot clot correctly and the person can have bleeding. On the other hand, if a person has genes that prevent enough warfarin from getting into the bloodstream, the person could develop serious blood clots. The way a person’s body reacts to warfarin, tamoxifen and other drugs depends on differences in their genetic makeup.
Genes provide your body with instructions for making enzymes. Enzymes are needed for your body to break down drugs so your body can get benefit from the medicine. You carry two copies of every gene: one from your mother and one from your father. Differences in these genes can affect the speed of different enzymes you have in your body. This affects how well your body is able to use medicines and how well drugs work in your body. Differences in your enzymes can affect how your body can metabolize (break down) a drug and how long the drug stays your body. Based on what type of genes you carry, you may be:
- a poor drug metabolizer
If you are a “poor metabolizer”, you do not break down drugs well. This may result in too much drug in the body which may lead to a dangerous side effect or even death. In some cases, your body may not be able to break down certain drugs to their working form and therefore the drugs will not work properly.
- an extensive or “normal” drug metbolizer
You metabolize drugs at the normal rate.
- an ultra-rapid drug metabolizer
If you are an “ultra-rapid” metabolizer, this means you break down drugs too fast, causing them to be of no use in the body. If medications do not work properly, conditions such as high blood pressure, blood disorders, and cancer will be left untreated and may even lead to death.
Genetic Tests for Drug Response
Researchers have now found more than 30 types of drug metabolizing enzymes in humans and mostly all of them vary between people.
The three main genetic tests available today include: CYP2D6, CYP2C9, and CYP2C1.
Read entire article at: Consumer Health
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Pharmacists Play Key Role In Pharmacogenetics
Pharmacists may play a key role in applying pharmacogenetic discoveries to patient care.
Application of pharmacogenetic discoveries requires knowledge and understanding of the disposition and pharmacodynamics of drugs. Additionally, a good understanding of clinical factors that can influence pharmacokinetics and pharmacodynamics of drugs is also important in the effective application of pharmacogenetic discoveries to patient care.
Because pharmacists are experts in pharmacokinetics and pharmacodynamics, they can take a lead in application of pharmacogenetics in clinical practice. For example, NACB draft guidelines suggest that pharmacists may be engaged in interpreting pharmacogenetic testing results. In addition, some experts have suggested that pharmacists need access to patients’ genetic information in order to provide individualized pharmaceutical care before they fill prescriptions.
Although such involvement would require regulations and systems that secure and maintain patient confidentiality, the application of pharmacogenetics in clinical practice presents an opportunity where pharmacists can expand their roles in the genomic era. ~Medscape.com~
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Genetics and Genomics: Do you know the difference?
What are genetics and genomics?
Genetics is a term that refers to the study of genes and their roles in inheritance – in other words, the way that certain traits or conditions are passed down from one generation to another. Genetics involves scientific studies of genes and their effects. Genes (units of heredity) carry the instructions for making proteins, which direct the activities of cells and functions of the body. Examples of genetic or inherited disorders include cystic fibrosis (See: Learning About Cystic Fibrosis), Huntington’s disease (Learning About Huntington’s Disease), and phenylketonuria (PKU) (Learning About Phenylketonuria).
Genomics is a more recent term that describes the study of all of a person’s genes (the genome), including interactions of those genes with each other and with the person’s environment. Genomics includes the scientific study of complex diseases such as heart disease, asthma, diabetes, and cancer because these diseases are typically caused more by a combination of genetic and environmental factors than by individual genes. Genomics is offering new possibilities for therapies and treatments for some complex diseases, as well as new diagnostic methods.
Pharmacogenetics and Pharmacogenomics
The terms “pharmacogenetics” and “pharmacogenomics” are often used interchangeably in describing the intersection of pharmacology (the study of drugs, or pharmaceuticals) and genetic variability in determining an individual’s response to particular drugs. The terms may be distinguished in the following way.
Pharmacogenetics is the field of study dealing with the variability of responses to medications due to variation in single genes. Pharmacogenetics takes into account a person’s genetic information regarding specific drug receptors and how drugs are transported and metabolized by the body. The goal of pharmacogenetics is to create an individualized drug therapy that allows for the best choice and dose of drugs. One example is the breast cancer drug trastuzumab (Herceptin). This therapy works only for women whose tumors have a particular genetic profile that leads to overproduction of a protein called HER2. (See: Genetics, Disease Prevention and Treatment)
Pharmacogenomics is similar to pharmacogenetics, except that it typically involves the search for variations in multiple genes that are associated with variability in drug response. Since pharmacogenomics is one of the large-scale “omic” technologies, it can examine the entirety of the genome, rather than just single genes. Pharmacogenomic studies may also examine genetic variation among large groups of people (populations), for example, in order to see how different drugs might affect different racial or ethnic groups.
Pharmacogenetic and pharmacogenomic studies are leading to drugs that can be tailor-made for individuals, and adapted to each person’s particular genetic makeup. Although a person’s environment, diet, age, lifestyle, and state of health can also influence that person’s response to medicines, understanding an individual’s genetic makeup is key to creating personalized drugs that work better and have fewer side effects than the one-size-fits-all drugs that are common today. (See: Genetics, Disease Prevention and Treatment). For example, the U.S. Food and Drug Administration (FDA) recommends genetic testing before giving the chemotherapy drug mercaptopurine (Purinethol) to patients with acute lymphoblastic leukemia. Some people have a genetic variant that interferes with their ability to process this drug. This processing problem can cause severe side effects, unless the standard dose is adjusted according to the patient’s genetic makeup. (See: Frequently Asked Questions about Pharmacogenomics).
Read more at: genome.gov
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Personalized Medicine
What is Personalized Medicine?
To “personalize” or identify the preferred treatment options for individual patients, doctors typically consider a patient’s health, family history and other factors such as diet or lifestyle.
Advances in science and technology have made it possible to add one more piece to the puzzle: genetic variations that influence how a patient responds to certain medicines.
In recent years, the U.S. Food and Drug Administration began revising labeling guidelines for certain medications to inform doctors and patients about genetic variations that can affect the body’s response to a drug. Screening for genetic variations can help patients receive the proper dosage, experience fewer side effects or avoid drugs that might not work well.
Read more at: UFHealth.com
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What is Pharmacogenetics?
A person’s environment, diet, and general state of health can all influence how he or she responds to medicines. But another key factor is genes. The study of how people respond differently to medicines due to their genetic inheritance is called pharmacogenetics. The term has been pieced together from the words pharmacology (the study of how drugs work in the body) and genetics (the study of how traits are inherited). An ultimate goal of pharmacogenetics is to understand how someone’s genetic make-up determines how well a medicine works in his or her body, as well as what side effects are likely to occur. In the future, advances gleaned from pharmacogenetics research will provide information to guide doctors in getting just enough of the right medicine to a person–the practice of “personalized medicine.”
Read more at: Dartmouth.edu
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Primary Care and Pharmacogenetic Testing
Pharmacogenetic (PGx) testing is a type of genetic test that assesses a patient’s risk of an adverse response or likelihood to respond to a given drug, informing drug selection and dosing.
As a pillar of the personalized medicine movement, PGx testing is anticipated to be important across all medical specialties,2 but particularly in primary care, where the majority of all drug prescriptions are written. It has been estimated that many of the drugs commonly prescribed by primary care practitioners (PCPs) such as fluoxetine, metoprolol, warfarin, and simvastatin are affected by PGx variation. Although several different strategies of delivering PGx testing have been proposed or are being investigated,6–8 at present, there is little clarity on which health professionals should order PGx testing, at what stage during treatment testing should be ordered, how best to communicate results to patients, and where results should be stored to inform future therapeutic decision making. Patients prefer receiving PGx test results from a familiar provider whom they trust such as a PCP; however, several factors have contributed to the slow integration of PGx testing in the primary care setting, including limited time as well as familiarity and experience with PGx testing. Because PGx testing is a relatively new field and many PCPs are unfamiliar with many of the basic tenets of the field, ongoing learning opportunities and/or faculty development would enable PCPs to feel more comfortable with the topic, and presumably engage in more effective communication with patients, and more appropriate use of testing. This paper suggests key elements to be discussed with patients prior to testing and when reporting test results to assist PCPs while recognizing some of the practical limitations in the primary care setting.
Read entire article here
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